Congressional is one of 12 cemeteries in the District still accepting new residents alongside people such as Civil War photographer Mathew Brady. But choosing a site for a new burial isn’t always a sure bet. Over time, headstones go missing and records disappear. The cemetery hasn’t had a comprehensive map made of its holdings since 1935. Using carefully calibrated radar, Perry (“Bone Finder”) is able to find open space for the cemetery as well as provide a more detailed picture of the bodies buried there.

Ground-penetrating radar was first put to use in the Vietnam War. Perry remembers seeing it even though he didn’t realize what it was at the time. Perry worked on river patrol boats, sometimes carrying elite forces up and down the waterways.

One day, after dropping a crew off, he stopped at an outpost to get something to eat. “I happened to see these guys on the ground pulling this piece of equipment around, and it never dawned on me what it was.” Years later, he realized that they were searching for enemy cells using the same technology he now uses.

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